Pituitary studies: The human hypophysis will be investigated (with special staining techniques, electron microscopy, light- and electron-microscopic immunocytochemistry) to establish the ultrastructure of functionally characterized cell types, to identify the hormones stored in FSH-LH, MSH-ACTH, gamma and chromophobic adenoma cell granules, to explore the response of gonadotrops to ovarian senescence, and to contrast the function of posterior lobe and anterior lobe ACTH-MSH cells. Thyroid studies: a) The effect of in vivo stimulation by TSH will be studied in rat thyroids with respect to quantitative and possible qualitative changes in the adenylate cyclase to protein kinase sequence (cyclase, cyclic AMP concentration, cyclic AMP-receptor protein interaction and associated activation of protein kinase, subcellular translocation of this kinase). b) The kinetics of iodide transport will be investigated in isolated thyroid cells to corroborate evidence pointing to exit by an energy-dependent, saturatable process, separate regulation of iodide entry and exit by TSH, and (possibly cyclic AMP-mediated) effects of TSH on iodide transport secondary to stimulated endocytosis.